During the previous period of support, we have introduced, explored, and developed an approach to motor synergies based on the principle of abundance and using the computational tools of the uncontrolled manifold hypothesis. Now we suggest focusing on three major goals. First, we plan to analyze interaction of synergies at different levels of a control hierarchy. Second, we will explore the purposes and benefits of using synergic control to move closer to application of these ideas to everyday movements and disordered movements. Third, we will explore differences between the synergies involved in two basic classes of actions, discrete and cyclic. The planned experiments will address the following main questions: What is the purpose of synergies? How do synergies at different levels of a control hierarchy interact with each other? Are there qualitative differences in the synergic mechanisms during cyclic and discrete actions? We will perform eight experiments using several of the novel experimental devices constructed in our group, such as the inverse piano, the collapsing cup, and the handle with spring-loaded sensors. Each experiment will test 2-4 specific hypotheses. The long-term goal of this research is to develop a coherent theoretical view on and advance the current understanding of how natural multieffector human movements are controlled and coordinated. Developing such a view would have a profound impact on the practice of preventing and treating motor disorders. These studies will also contribute to developing a toolbox to study motor synergies during both unimpaired and disordered movements. PUBLIC HEALTH RELEVANCE: The overarching goal of the proposed research is to advance the current understanding of the organization, purposes, and benefits of synergic control of movements. We plan to move closer to application of these ideas to everyday motor tasks and disordered movements. At the same time, we are developing a toolbox to study motor synergies; such a toolbox may be applied to both unimpaired and disordered movements.